Ionotropic chemosensory receptors expressed in insect olfactory and gustatory systems

Abstract

  Chemosensory system recognizes more than 100,000 chemical compounds in the environment. Animals have evolved the diverse chemoreceptor gene families, which allow the recognition of infinitely many chemicals. In vertebrates, most of chemoreceptors belong to the family of G-protein coupled receptors possessing seven-transmembrane domains. Thus, binding of ligand and receptors results in activation of G-protein signaling pathways and downstream ion channels. Although insect olfactory and gustatory receptors have been reported as the member of G-protein coupled receptors, recent progress in the functional expression of insect chemoreceptors revealed the conformation of ligand-gated ion channel by olfactory and gustatory receptors. The activity of these ion channels is independent of known G-protein signaling pathways. Genome analysis of fruit flys also has revealed the diverse ionotropic glutamate receptor-related gene families function as the chemoreceptor. In this review, I discuss some of the molecular mechanism underlying the insect chemosensory systems, with a particular focus on the function of chemosensory receptor-channels.